Apparatus for testing gas-locks



Apwfill 129% H g n/ APPARATUS FOR TESTING GAS LOCKS Filed Nov. 26, 1952 //.L. SM/ 77/ INVENTON Ext w ms ATTORNEY atented Apr. 28, 1936 APPARATUS FOR, TESTING GAS-LOCKS Harry L. Smith, Long Beach, Caliil, assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application November 26, 1932, Serial No. 644,509

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My invention relates to the testing of motor fuels and more particularly to apparatus for testing a fuel such as gasoline to determine its tendency to vapor-lock when used in the power plant of an internal combustion engine.

The objectionable feature of vapor-locking lies in the loss of power in the engine using the fuel and other attendant effects, due to the excessively lean air-fuel mixture produced in the carit) buretor, this leanness being caused by the passage of bubbles of vapor through the metering jet of the carburetor. Vapor-lock is without doubt one of the most elusive and difficult to measure of all the characteristics of motor fuels and this difiiculty is due mainly to the number and nature of the many variables which effect this phenomena. These variables may be divided into; first, characteristics of the gasoline; second, design and operating characteristics of the engine 0 in which the vapor-locking occurs.

It is manifestly impractical to cover all the possible combinations of variables in measuring the vapor-locking tendency of each fuel, especially in the case of semi-routine tests. Further- 515 more, it is, of course, impossible to control the variables in the second class as presented by the large variety of internal combustion engines on the market.

For these reasons I have provided an appara- 30 tus which is susceptive to accurate control and capable of producing vapor-lock in any usual motor fuel and which at the same time is as nearly comparable with the actual motor car operating conditions as is consistent with these aims.

In carrying out my invention I have mounted a mixing or carbureting device in a heat insulated chamber and have provided means for controlling the temperatures of the air and fuel taken into the carburetor together with means 40 for accurately measuring these temperatures as well as the temperature of the gas mixture at the fuel jet within the carburetor. The arrangement is such that any vapor forming in the fuel line leading to the jet of the carbureting device will of necessity pass through the jet, thus causing excessive leanness with a decrease in power in the engine operated on the mixture containing the fuel being tested.

For a better understanding of my invention,

50 reference may be had to the accompanying drawing wherein the single figure shows a somewhat diagrammatic vertical section of an apparatus embodying my invention.

The apparatus as shown in the drawing consists of an air-fuel mixing device or carburetor it enclosed in a suitable, preferably heat insulated, casing ll somewhat similar to the ordinary constant temperature laboratory oven. The chamber IZ formed by the casing It may be maintained at a temperature of any desired degree by electric heating coils I3 placed near the lower wall of the casing. The heat from these coils is evenly diffused by a perforated grid M, located directly above them. The air temperature in the chamber I2 is indicated by a thermometer Mia or, if desired, a suitable thermocouple.

The air-fuel mixing device it] consists of an air passage provided with a Venturi tube iii in which is located a jet l6 for the fuel supply.

The air entering the carburetor or mixer is is heated to the desired degree by an electric heater i I placed in the air intake tube i8, preferably outside of the casing H. The air temperature in the tube l8, as wellas that of the airfuel mixture, may be measured by suitably placed thermocouples i9 and 20 connected to sensitive galvanometers of voltmeters Ma and 20a.

The flow of air-fuel mixture leaving the carbureting device if! is regulated by a butterfly throttle valve 2i which is arranged to be operated from the outside of the casing it while the pressure and volume of the air entering the intake may be regulated by a similar throttle valve 22 placed in the inlet tube I8. The pressure of the air entering the intake is indicated by a manometer 22a connected to the air inlet tube i8 by means of a small tube 23. A second manometer, not shown, is attached to the engine intake. The flow of the fuel is regulated by a needle valve 24 inserted in the fuel passage in the usual manner.

The fuel supply for the jet i6 is obtained from a constant level float bowl 25 of the usual type located on the outside of the casing i i, which is in turn connected by a tube 25a to a source of supply of the fuel under test. The fuel leaving the float bowl flows to the jet 16 through a metallic tube, preferably of copper, a portion of which is Wound in the form of a helical coil 26 rising toward the jet. The purpose of the coil 26 is to allow the temperature of the fuel entering the carburetor IE] to be brought to that of the air in the heating chamber E2. The temperature of the fuel leaving the jet is indicated by a thermocouple 21 located as near the top of the jet as possible and connected to a suitable galvanometer or voltmeter 21a. The air pressure above the fuel in the float bowl 25 and the jet I6 is equalized through a small tube 28.

The air-fuel mixture leaves the carburetor ll) through a pipe 29, preferably of brass, which is connected to the intake of any desired internal combustion engine, not shown, preferably mounted on a chassis dynamometer, with provision for measuring the power output and maintaining all other factors constant.

Previous to the actual vapor-lock tests the engine is operated until the inlet air temperature and pressure-manifold vacuum at the intake of engine, cooling water temperature, speed and approximate power output, are all constant. The fuel under test is then connected to the float bowl 25 and the mixture ratio adjusted with the needle valve 24 until the power output reaches a predetermined value, maintaining at the same time all the above enumerated constants. Under these conditions, the power output is a measure of the effective mixture ratio entering the engine. The power output is selected so that the corresponding mixture ratio is at that point where any further decrease in fuel will cause a sharp drop in power. The exact value of this ratio may be determined, if desired, by metering both the air and fuel supply.

While the engine is operating as thus described, the temperature of the air in the casing H is raised gradually by means of the heating coils i3 until a sudden drop in power output occurs, as shown by the dynamometer scales. The temperature of the gasoline leaving the jet H5 at this point, as evidenced by means of the thermocouple 2! and meter 21a, is recorded as a measure of the vapor-locking tendency of the fuel under test. Usually at least three consecutive check runs are made, and the average figure recorded.

The design of the apparatus as shown on the attached drawing may, of course, be varied considerably without effecting the fundamental features. For instance, the mixing device shown may be replaced with an ordinary carburetor. However, the results obtained in this way are sometimes erratic owing to the vaporization of the gasoline in the float bowl. For this reason the float bowl has been placed, as shown in the drawing, on the outside of the chamber I2. The copper helix 26 serves to raise the incoming fuel to the temperature of the surrounding air and any vapor produced in this coil or in the passages in the mixer I0 is forced to exit through the jet H3, thereby producing the decrease in power mentioned hereinbefore.

If a curve is made on the particular engine in use, showing the variation in power with changes in mixture ratio, it is possible to determine the actual volume of vapor which is necessary to produce the symptoms of vapor-lock.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In an apparatus for testing the vapor-locking tendencies of motor fuels, a casing forming a heating chamber, a carbureting device within said chamber and comprising an air intake tube, a Venturi tube, and a fuel supply jet located within said Venturi tube, an outlet tube for conducting the air-fuel mixture from said carburetor to an internal combustion engine, means for heating the interior of said chamber and the fuel entering said fuel supply jet, separate means for heating the air entering said air intake tube, a pressure measuring device connected to said air intake tube and temperature measuring devices connected to said air intake tube, said outlet tube and said fuel supply jet.

2. In an apparatus for testing the vapor-locking tendencies of motor fuels, a casing forming an enclosed heating chamber, a carbureting device mounted within said chamber and having an air intake, a source of fuel supply, a connection between said fuel supply and said carbureting device, an outlet conduit for conducting the combustible mixture from said carbureting device, an electric heating device located at the bottom of said chamber, a heat diffusing member located between said heating device and said carbureting device, means external to said chamber for heating air passing through said air intake, means for measuring the pressure in said air intake, and means for measuring the temperatures in said chamber, said carbureting device and said outlet conduit.

3. In an apparatus for testing the vapor-locking tendencies of motor fuels, a casing forming an enclosed heating chamber, a device within said chamber for forming a combustible mixture of air and a liquid fuel comprising an air intake tube, a Venturi tube and a fuel supply jet located within said Venturi tube, an outlet tube for conducting the combustible mixture from said mixing device, means for heating the interior of said chamber and the fuel entering said fuel supply jet, separate means for heating the air entering said air intake tube, a pressure measuring device connected to said air intake tube, means for controlling the pressure and volume of air passing through said intake tube, means for controlling the flow of combustible mixture through said outlet tube, and temperature measuring devices connected to said air intake tube, said outlet tube, said fuel supply jet and the interior of said cas- 4. In an apparatus for testing the vapor-locking tendencies of motor fuels, a casing forming a heating chamber, a mixing device within said chamber and having an air intake, a source of fuel supply, a float bowl mounted outside of said chamber and connected to said fuel supply source, a conduit connecting said float bowl with said mixing device, said conduit including a helical portion within said chamber leading upwardly to said mixing device, means for equalizing the pressures in said mixing device and in the upper part of said float bowl, an outlet conduit for conducting the air-fuel mixture from said mixing device to an internal combustion engine, means within said chamber for maintaining a predetermined temperature therein, means external to said chamber for heating the air passing through said air intake, a pressure measuring device connected to said air intake, and temperature measuring devices connected to said chamber, said mixing device, and said outlet conduit.

HARRY L. SMITH. 

